Cellulosic fibrous structures are a staple of everyday life. Cellulosic fibrous structures are used as consumer products for paper towels, toilet tissue, facial tissue, napkins and the like. The large demand for such paper products has created a demand for improved versions of the products and the methods of their manufacture.
Multiple ply cellulosic fibrous structures are very well known in the art of consumer products. Such products are cellulosic fibrous structures having more than one, typically two, plies superimposed in face-to-face relationship to form a laminate. It is known in the art to emboss sheets comprising multiple plies of tissue for aesthetic purposes and to maintain the plies in face-to-face relation during use. In addition, embossing can increase the surface area of the plies thereby enhancing their bulk and water holding capacity.
During the embossing process, the plies are fed through a nip formed between juxtaposed axially parallel rolls. Embossment knobs on these rolls compress like regions of each ply into engagement and contacting relationship with the opposing ply. The compressed regions of the plies produce an aesthetic pattern and provide a means for joining and maintaining the plies in face-to-face contacting relationship.
Embossing is typically performed by one of two processes, knob-to-knob embossing or nested embossing. Knob-to-knob embossing consists of axially parallel rolls juxtaposed to form a nip between the knobs on opposing rolls. Nested embossing consists of embossment knobs of one roll meshed between the embossment knobs of the other roll. Examples of knob-to-knob embossing and nested embossing are illustrated in the prior art by U.S. Pat. Nos. 3,414,459 issued Dec. 3, 1968 to Wells and commonly assigned; U.S. Pat. No. 3,547,723 issued Dec. 15, 1970 to Gresham; U.S. Pat. No. 3,556,907 issued Jan. 19, 1971 to Nystrand; U.S. Pat. No. 3,708,366 issued Jan. 2, 1973 to Donnelly; U.S. Pat. No. 3,738,905 issued Jun. 12, 1973 to Thomas; U.S. Pat. No. 3,867,225 issued Feb. 18, 1975 to Nystrand and U.S. Pat. No. 4,483,728 issued Nov. 20, 1984 to Bauernfeind.
Knob to knob embossing produces a cellulosic fibrous structure composed of pillowed regions which enhance the thickness of the product. However, the pillows have a tendency to collapse under pressure due to lack of support. Consequently, the thickness benefit is typically lost during the balance of the converting operation and subsequent packaging, diminishing the quilted appearance sought by embossing.
Nested embossing has proven to be the preferred process for producing products exhibiting a softer more quilted appearance that is maintained throughout the balance of the converting process including packaging. With nested embossing, one ply has a male pattern, while the other ply has a female pattern. As the two plies travel through the nip of the embossment rolls, the patterns are meshed together. Nested embossing aligns the knob crests on the male embossment roll with the low areas on the female embossment roll. As a result, the embossed sites produced on one ply provide support for the embossed sites on the other ply.
The lamination point at the nip between nested embossment rolls is typically eliminated, since the knobs on the nested embossment rolls do not touch. This necessitates the addition of a marrying roll to apply pressure for lamination. Typical marrying rolls are solid resulting in the lamination of every potential laminating point as shown in U.S. Pat. No. 3,867,225 issued Feb. 18, 1975 to Nystrand.
The nested embossment rolls may be designed such that the knobs on one roll contact the periphery of the other embossing roll providing a lamination point, thereby eliminating the need for a marrying roll. Such nested embossing arrangement is shown in U.S. Pat. No. 5,468,323 issued Nov. 21, 1995 to McNeil. This arrangement also provides a means for improving the bond strength between the plies by enabling a glue applicator roll to be used in conjunction with each of the embossment rolls providing an adhesive joint at each of the embossed sites.
Consumer testing of products having embossed cellulosic fibrous structures have determined that a softer, more quilted appearance is desired. Consumers desire products having relatively high caliper with aesthetically pleasing decorative patterns exhibiting a high quality cloth-like appearance. Such attributes must be provided without sacrificing the products' other desired qualities of softness, absorbency, drape (limpness) and bond strength between the plies.
Different attempts have been made in the art to produce paper products exhibiting superior functional properties as well as aesthetically pleasing decorative qualities. The present invention provides an embossed multiple ply tissue where the embossment patterns on each of the two plies are designed with specific objectives in mind. For instance, the embossed pattern on the first ply is based primarily on aesthetics while the embossed pattern on the second ply is based primarily on functional properties such as thickness and strength. In addition, the quantity and locations of the connections between the two plies are limited in order to coordinate the bond strength between the two plies with softness and drape of the final product.